His DTMF decoder box uses a CM8870 DTMF decoder chip ... This was well and good, but he decided that an Arduino-driven LCD display would work far better. When he was finished, he had a compact ...

The project uses a DRA818 VHF/UHF transceiver plugged into a low-pass filter combined with a hardware DTMF decoder ... the level shifter he used on the Arduino’s 5 V data didn’t work as ...